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        <li class="chapter " data-level="1.1" data-path="../../">
            
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                    Introduction
            
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        <li class="chapter " data-level="1.2" data-path="tutorials/">
            
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                    快速上手
            
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        <li class="chapter " data-level="1.2.1" data-path="tutorials/TypeScript in 5 minutes.html">
            
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                    5分钟了解TypeScript
            
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        <li class="chapter " data-level="1.2.2" data-path="tutorials/ASP.NET Core.html">
            
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                    ASP.NET Core
            
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                    ASP.NET 4
            
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                    Gulp
            
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        <li class="chapter " data-level="1.2.5" data-path="tutorials/Knockout.html">
            
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                    Knockout.js
            
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                    React与webpack
            
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                    React
            
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                    Angular 2
            
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                    从JavaScript迁移到TypeScript
            
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                    手册
            
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                    基础类型
            
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                    变量声明
            
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                    接口
            
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                    类
            
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                    函数
            
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                    泛型
            
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                    枚举
            
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        <li class="chapter active" data-level="1.3.8" data-path="Type Inference.html">
            
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                    类型推论
            
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        <li class="chapter " data-level="1.3.9" data-path="Type Compatibility.html">
            
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                    类型兼容性
            
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        <li class="chapter " data-level="1.3.10" data-path="Advanced Types.html">
            
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                    高级类型
            
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        <li class="chapter " data-level="1.3.11" data-path="Utilit Types.md">
            
                <span>
            
                    
                    实用工具类型
            
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                    Symbols
            
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        <li class="chapter " data-level="1.3.13" data-path="Iterators and Generators.html">
            
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                    Iterators 和 Generators
            
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        <li class="chapter " data-level="1.3.14" data-path="Modules.html">
            
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                    模块
            
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        <li class="chapter " data-level="1.3.15" data-path="Namespaces.html">
            
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                    命名空间
            
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        <li class="chapter " data-level="1.3.16" data-path="Namespaces and Modules.html">
            
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                    命名空间和模块
            
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        <li class="chapter " data-level="1.3.17" data-path="Module Resolution.html">
            
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                    模块解析
            
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        <li class="chapter " data-level="1.3.18" data-path="Declaration Merging.html">
            
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                    声明合并
            
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        <li class="chapter " data-level="1.3.19" data-path="Writing Definition Files.html">
            
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                    书写.d.ts文件
            
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                    JSX
            
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        <li class="chapter " data-level="1.3.21" data-path="Decorators.html">
            
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                    Decorators
            
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        <li class="chapter " data-level="1.3.22" data-path="Mixins.html">
            
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                    混入
            
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        <li class="chapter " data-level="1.3.23" data-path="Triple-Slash Directives.html">
            
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                    三斜线指令
            
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        <li class="chapter " data-level="1.3.24" data-path="Type Checking JavaScript Files.html">
            
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                    JavaScript文件里的类型检查
            
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        <li class="chapter " data-level="1.4" data-path="declaration files/Introduction.html">
            
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                    如何书写声明文件
            
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                    结构
            
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        <li class="chapter " data-level="1.4.2" data-path="declaration files/Do's and Don'ts.html">
            
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                    规范
            
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        <li class="chapter " data-level="1.4.3" data-path="declaration files/By Example.html">
            
                <a href="declaration files/By Example.html">
            
                    
                    举例
            
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        <li class="chapter " data-level="1.4.4" data-path="declaration files/Deep Dive.html">
            
                <a href="declaration files/Deep Dive.html">
            
                    
                    深入
            
                </a>
            

            
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        <li class="chapter " data-level="1.4.5" data-path="declaration files/Publishing.html">
            
                <a href="declaration files/Publishing.html">
            
                    
                    发布
            
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        <li class="chapter " data-level="1.4.6" data-path="declaration files/Consumption.html">
            
                <a href="declaration files/Consumption.html">
            
                    
                    使用
            
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            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.5" data-path="tsconfig.json.html">
            
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                    工程配置
            
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        <li class="chapter " data-level="1.5.1" data-path="tsconfig.json.html">
            
                <a href="tsconfig.json.html">
            
                    
                    tsconfig.json
            
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        <li class="chapter " data-level="1.5.2" data-path="Project References.html">
            
                <a href="Project References.html">
            
                    
                    工程引用
            
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        <li class="chapter " data-level="1.5.3" data-path="Typings for NPM Packages.html">
            
                <a href="Typings for NPM Packages.html">
            
                    
                    NPM包的类型
            
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        </li>
    
        <li class="chapter " data-level="1.5.4" data-path="Compiler Options.html">
            
                <a href="Compiler Options.html">
            
                    
                    编译选项
            
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        <li class="chapter " data-level="1.5.5" data-path="Configuring Watch.html">
            
                <a href="Configuring Watch.html">
            
                    
                    配置 Watch
            
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        <li class="chapter " data-level="1.5.6" data-path="Compiler Options in MSBuild.html">
            
                <a href="Compiler Options in MSBuild.html">
            
                    
                    在MSBuild里使用编译选项
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.5.7" data-path="Integrating with Build Tools.html">
            
                <a href="Integrating with Build Tools.html">
            
                    
                    与其它构建工具整合
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.5.8" data-path="Nightly Builds.html">
            
                <a href="Nightly Builds.html">
            
                    
                    使用TypeScript的每日构建版本
            
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        </li>
    

            </ul>
            
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        <li class="chapter " data-level="1.6" data-path="../wiki/">
            
                <a href="../wiki/">
            
                    
                    Wiki
            
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        <li class="chapter " data-level="1.6.1" data-path="../wiki/this-in-TypeScript.html">
            
                <a href="../wiki/this-in-TypeScript.html">
            
                    
                    TypeScript里的this
            
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        <li class="chapter " data-level="1.6.2" data-path="../wiki/coding_guidelines.html">
            
                <a href="../wiki/coding_guidelines.html">
            
                    
                    编码规范
            
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        <li class="chapter " data-level="1.6.3" data-path="../wiki/Common Errors.html">
            
                <a href="../wiki/Common Errors.html">
            
                    
                    常见编译错误
            
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        <li class="chapter " data-level="1.6.4" data-path="../wiki/TypeScript-Editor-Support.html">
            
                <a href="../wiki/TypeScript-Editor-Support.html">
            
                    
                    支持TypeScript的编辑器
            
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        <li class="chapter " data-level="1.6.5" data-path="../wiki/Using-TypeScript-With-ASP.NET-5.html">
            
                <a href="../wiki/Using-TypeScript-With-ASP.NET-5.html">
            
                    
                    结合ASP.NET v5使用TypeScript
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.6" data-path="../wiki/Architectural-Overview.html">
            
                <a href="../wiki/Architectural-Overview.html">
            
                    
                    架构概述
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.7" data-path="../wiki/Roadmap.html">
            
                <a href="../wiki/Roadmap.html">
            
                    
                    发展路线图
            
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        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.7" data-path="../release-notes/">
            
                <a href="../release-notes/">
            
                    
                    新增功能
            
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            <ul class="articles">
                
    
        <li class="chapter " data-level="1.7.1" data-path="../release-notes/TypeScript 3.1.html">
            
                <a href="../release-notes/TypeScript 3.1.html">
            
                    
                    TypeScript 3.1
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.2" data-path="../release-notes/TypeScript 3.0.html">
            
                <a href="../release-notes/TypeScript 3.0.html">
            
                    
                    TypeScript 3.0
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.3" data-path="../release-notes/TypeScript 2.9.html">
            
                <a href="../release-notes/TypeScript 2.9.html">
            
                    
                    TypeScript 2.9
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.4" data-path="../release-notes/TypeScript 2.8.html">
            
                <a href="../release-notes/TypeScript 2.8.html">
            
                    
                    TypeScript 2.8
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.5" data-path="../release-notes/TypeScript 2.7.html">
            
                <a href="../release-notes/TypeScript 2.7.html">
            
                    
                    TypeScript 2.7
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.6" data-path="../release-notes/TypeScript 2.6.html">
            
                <a href="../release-notes/TypeScript 2.6.html">
            
                    
                    TypeScript 2.6
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.7" data-path="../release-notes/TypeScript 2.5.html">
            
                <a href="../release-notes/TypeScript 2.5.html">
            
                    
                    TypeScript 2.5
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.8" data-path="../release-notes/TypeScript 2.4.html">
            
                <a href="../release-notes/TypeScript 2.4.html">
            
                    
                    TypeScript 2.4
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.9" data-path="../release-notes/TypeScript 2.3.html">
            
                <a href="../release-notes/TypeScript 2.3.html">
            
                    
                    TypeScript 2.3
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.10" data-path="../release-notes/TypeScript 2.2.html">
            
                <a href="../release-notes/TypeScript 2.2.html">
            
                    
                    TypeScript 2.2
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.11" data-path="../release-notes/TypeScript 2.1.html">
            
                <a href="../release-notes/TypeScript 2.1.html">
            
                    
                    TypeScript 2.1
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.12" data-path="../release-notes/TypeScript 2.0.html">
            
                <a href="../release-notes/TypeScript 2.0.html">
            
                    
                    TypeScript 2.0
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.13" data-path="../release-notes/TypeScript 1.8.html">
            
                <a href="../release-notes/TypeScript 1.8.html">
            
                    
                    TypeScript 1.8
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.14" data-path="../release-notes/TypeScript 1.7.html">
            
                <a href="../release-notes/TypeScript 1.7.html">
            
                    
                    TypeScript 1.7
            
                </a>
            

            
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        <li class="chapter " data-level="1.7.15" data-path="../release-notes/TypeScript 1.6.html">
            
                <a href="../release-notes/TypeScript 1.6.html">
            
                    
                    TypeScript 1.6
            
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        <li class="chapter " data-level="1.7.16" data-path="../release-notes/TypeScript 1.5.html">
            
                <a href="../release-notes/TypeScript 1.5.html">
            
                    
                    TypeScript 1.5
            
                </a>
            

            
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        <li class="chapter " data-level="1.7.17" data-path="../release-notes/TypeScript 1.4.html">
            
                <a href="../release-notes/TypeScript 1.4.html">
            
                    
                    TypeScript 1.4
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.18" data-path="../release-notes/TypeScript 1.3.html">
            
                <a href="../release-notes/TypeScript 1.3.html">
            
                    
                    TypeScript 1.3
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.19" data-path="../release-notes/TypeScript 1.1.html">
            
                <a href="../release-notes/TypeScript 1.1.html">
            
                    
                    TypeScript 1.1
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.8" data-path="../breaking-changes/breaking-changes.html">
            
                <a href="../breaking-changes/breaking-changes.html">
            
                    
                    Breaking Changes
            
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            <ul class="articles">
                
    
        <li class="chapter " data-level="1.8.1" data-path="../breaking-changes/TypeScript 2.4.html">
            
                <a href="../breaking-changes/TypeScript 2.4.html">
            
                    
                    TypeScript 2.4
            
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        <li class="chapter " data-level="1.8.2" data-path="../breaking-changes/TypeScript 2.3.html">
            
                <a href="../breaking-changes/TypeScript 2.3.html">
            
                    
                    TypeScript 2.3
            
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        <li class="chapter " data-level="1.8.3" data-path="../breaking-changes/TypeScript 2.2.html">
            
                <a href="../breaking-changes/TypeScript 2.2.html">
            
                    
                    TypeScript 2.2
            
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        <li class="chapter " data-level="1.8.4" data-path="../breaking-changes/TypeScript 2.1.html">
            
                <a href="../breaking-changes/TypeScript 2.1.html">
            
                    
                    TypeScript 2.1
            
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        <li class="chapter " data-level="1.8.5" data-path="../breaking-changes/TypeScript 2.0.html">
            
                <a href="../breaking-changes/TypeScript 2.0.html">
            
                    
                    TypeScript 2.0
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.8.6" data-path="../breaking-changes/TypeScript 1.8.html">
            
                <a href="../breaking-changes/TypeScript 1.8.html">
            
                    
                    TypeScript 1.8
            
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        <li class="chapter " data-level="1.8.7" data-path="../breaking-changes/TypeScript 1.7.html">
            
                <a href="../breaking-changes/TypeScript 1.7.html">
            
                    
                    TypeScript 1.7
            
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        <li class="chapter " data-level="1.8.8" data-path="../breaking-changes/TypeScript 1.6.html">
            
                <a href="../breaking-changes/TypeScript 1.6.html">
            
                    
                    TypeScript 1.6
            
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        <li class="chapter " data-level="1.8.9" data-path="../breaking-changes/TypeScript 1.5.html">
            
                <a href="../breaking-changes/TypeScript 1.5.html">
            
                    
                    TypeScript 1.5
            
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        <a href="../.." >类型推论</a>
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                                <section class="normal markdown-section">
                                
                                <h1 id="&#x4ECB;&#x7ECD;">&#x4ECB;&#x7ECD;</h1>
<p>&#x8FD9;&#x8282;&#x4ECB;&#x7ECD;TypeScript&#x91CC;&#x7684;&#x7C7B;&#x578B;&#x63A8;&#x8BBA;&#x3002;&#x5373;&#xFF0C;&#x7C7B;&#x578B;&#x662F;&#x5728;&#x54EA;&#x91CC;&#x5982;&#x4F55;&#x88AB;&#x63A8;&#x65AD;&#x7684;&#x3002;</p>
<h1 id="&#x57FA;&#x7840;">&#x57FA;&#x7840;</h1>
<p>TypeScript&#x91CC;&#xFF0C;&#x5728;&#x6709;&#x4E9B;&#x6CA1;&#x6709;&#x660E;&#x786E;&#x6307;&#x51FA;&#x7C7B;&#x578B;&#x7684;&#x5730;&#x65B9;&#xFF0C;&#x7C7B;&#x578B;&#x63A8;&#x8BBA;&#x4F1A;&#x5E2E;&#x52A9;&#x63D0;&#x4F9B;&#x7C7B;&#x578B;&#x3002;&#x5982;&#x4E0B;&#x9762;&#x7684;&#x4F8B;&#x5B50;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">let</span> x = <span class="hljs-number">3</span>;
</code></pre>
<p>&#x53D8;&#x91CF;<code>x</code>&#x7684;&#x7C7B;&#x578B;&#x88AB;&#x63A8;&#x65AD;&#x4E3A;&#x6570;&#x5B57;&#x3002;
&#x8FD9;&#x79CD;&#x63A8;&#x65AD;&#x53D1;&#x751F;&#x5728;&#x521D;&#x59CB;&#x5316;&#x53D8;&#x91CF;&#x548C;&#x6210;&#x5458;&#xFF0C;&#x8BBE;&#x7F6E;&#x9ED8;&#x8BA4;&#x53C2;&#x6570;&#x503C;&#x548C;&#x51B3;&#x5B9A;&#x51FD;&#x6570;&#x8FD4;&#x56DE;&#x503C;&#x65F6;&#x3002;</p>
<p>&#x5927;&#x591A;&#x6570;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x7C7B;&#x578B;&#x63A8;&#x8BBA;&#x662F;&#x76F4;&#x622A;&#x4E86;&#x5F53;&#x5730;&#x3002;
&#x540E;&#x9762;&#x7684;&#x5C0F;&#x8282;&#xFF0C;&#x6211;&#x4EEC;&#x4F1A;&#x6D4F;&#x89C8;&#x7C7B;&#x578B;&#x63A8;&#x8BBA;&#x65F6;&#x7684;&#x7EC6;&#x5FAE;&#x5DEE;&#x522B;&#x3002;</p>
<h1 id="&#x6700;&#x4F73;&#x901A;&#x7528;&#x7C7B;&#x578B;">&#x6700;&#x4F73;&#x901A;&#x7528;&#x7C7B;&#x578B;</h1>
<p>&#x5F53;&#x9700;&#x8981;&#x4ECE;&#x51E0;&#x4E2A;&#x8868;&#x8FBE;&#x5F0F;&#x4E2D;&#x63A8;&#x65AD;&#x7C7B;&#x578B;&#x65F6;&#x5019;&#xFF0C;&#x4F1A;&#x4F7F;&#x7528;&#x8FD9;&#x4E9B;&#x8868;&#x8FBE;&#x5F0F;&#x7684;&#x7C7B;&#x578B;&#x6765;&#x63A8;&#x65AD;&#x51FA;&#x4E00;&#x4E2A;&#x6700;&#x5408;&#x9002;&#x7684;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x3002;&#x4F8B;&#x5982;&#xFF0C;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">let</span> x = [<span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-literal">null</span>];
</code></pre>
<p>&#x4E3A;&#x4E86;&#x63A8;&#x65AD;<code>x</code>&#x7684;&#x7C7B;&#x578B;&#xFF0C;&#x6211;&#x4EEC;&#x5FC5;&#x987B;&#x8003;&#x8651;&#x6240;&#x6709;&#x5143;&#x7D20;&#x7684;&#x7C7B;&#x578B;&#x3002;
&#x8FD9;&#x91CC;&#x6709;&#x4E24;&#x79CD;&#x9009;&#x62E9;&#xFF1A;<code>number</code>&#x548C;<code>null</code>&#x3002;
&#x8BA1;&#x7B97;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x7B97;&#x6CD5;&#x4F1A;&#x8003;&#x8651;&#x6240;&#x6709;&#x7684;&#x5019;&#x9009;&#x7C7B;&#x578B;&#xFF0C;&#x5E76;&#x7ED9;&#x51FA;&#x4E00;&#x4E2A;&#x517C;&#x5BB9;&#x6240;&#x6709;&#x5019;&#x9009;&#x7C7B;&#x578B;&#x7684;&#x7C7B;&#x578B;&#x3002;</p>
<p>&#x7531;&#x4E8E;&#x6700;&#x7EC8;&#x7684;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x53D6;&#x81EA;&#x5019;&#x9009;&#x7C7B;&#x578B;&#xFF0C;&#x6709;&#x4E9B;&#x65F6;&#x5019;&#x5019;&#x9009;&#x7C7B;&#x578B;&#x5171;&#x4EAB;&#x76F8;&#x540C;&#x7684;&#x901A;&#x7528;&#x7C7B;&#x578B;&#xFF0C;&#x4F46;&#x662F;&#x5374;&#x6CA1;&#x6709;&#x4E00;&#x4E2A;&#x7C7B;&#x578B;&#x80FD;&#x505A;&#x4E3A;&#x6240;&#x6709;&#x5019;&#x9009;&#x7C7B;&#x578B;&#x7684;&#x7C7B;&#x578B;&#x3002;&#x4F8B;&#x5982;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">let</span> zoo = [<span class="hljs-keyword">new</span> Rhino(), <span class="hljs-keyword">new</span> Elephant(), <span class="hljs-keyword">new</span> Snake()];
</code></pre>
<p>&#x8FD9;&#x91CC;&#xFF0C;&#x6211;&#x4EEC;&#x60F3;&#x8BA9;zoo&#x88AB;&#x63A8;&#x65AD;&#x4E3A;<code>Animal[]</code>&#x7C7B;&#x578B;&#xFF0C;&#x4F46;&#x662F;&#x8FD9;&#x4E2A;&#x6570;&#x7EC4;&#x91CC;&#x6CA1;&#x6709;&#x5BF9;&#x8C61;&#x662F;<code>Animal</code>&#x7C7B;&#x578B;&#x7684;&#xFF0C;&#x56E0;&#x6B64;&#x4E0D;&#x80FD;&#x63A8;&#x65AD;&#x51FA;&#x8FD9;&#x4E2A;&#x7ED3;&#x679C;&#x3002;
&#x4E3A;&#x4E86;&#x66F4;&#x6B63;&#xFF0C;&#x5F53;&#x5019;&#x9009;&#x7C7B;&#x578B;&#x4E0D;&#x80FD;&#x4F7F;&#x7528;&#x7684;&#x65F6;&#x5019;&#x6211;&#x4EEC;&#x9700;&#x8981;&#x660E;&#x786E;&#x7684;&#x6307;&#x51FA;&#x7C7B;&#x578B;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-keyword">let</span> zoo: Animal[] = [<span class="hljs-keyword">new</span> Rhino(), <span class="hljs-keyword">new</span> Elephant(), <span class="hljs-keyword">new</span> Snake()];
</code></pre>
<p>&#x5982;&#x679C;&#x6CA1;&#x6709;&#x627E;&#x5230;&#x6700;&#x4F73;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x7684;&#x8BDD;&#xFF0C;&#x7C7B;&#x578B;&#x63A8;&#x65AD;&#x7684;&#x7ED3;&#x679C;&#x4E3A;&#x8054;&#x5408;&#x6570;&#x7EC4;&#x7C7B;&#x578B;&#xFF0C;<code>(Rhino | Elephant | Snake)[]</code>&#x3002;</p>
<h1 id="&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;">&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;</h1>
<p>TypeScript&#x7C7B;&#x578B;&#x63A8;&#x8BBA;&#x4E5F;&#x53EF;&#x80FD;&#x6309;&#x7167;&#x76F8;&#x53CD;&#x7684;&#x65B9;&#x5411;&#x8FDB;&#x884C;&#x3002;
&#x8FD9;&#x88AB;&#x53EB;&#x505A;&#x201C;&#x6309;&#x4E0A;&#x4E0B;&#x6587;&#x5F52;&#x7C7B;&#x201D;&#x3002;&#x6309;&#x4E0A;&#x4E0B;&#x6587;&#x5F52;&#x7C7B;&#x4F1A;&#x53D1;&#x751F;&#x5728;&#x8868;&#x8FBE;&#x5F0F;&#x7684;&#x7C7B;&#x578B;&#x4E0E;&#x6240;&#x5904;&#x7684;&#x4F4D;&#x7F6E;&#x76F8;&#x5173;&#x65F6;&#x3002;&#x6BD4;&#x5982;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-built_in">window</span>.onmousedown = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">mouseEvent</span>) </span>{
    <span class="hljs-built_in">console</span>.log(mouseEvent.clickTime);  <span class="hljs-comment">//&lt;- Error</span>
};
</code></pre>
<p>&#x8FD9;&#x4E2A;&#x4F8B;&#x5B50;&#x4F1A;&#x5F97;&#x5230;&#x4E00;&#x4E2A;&#x7C7B;&#x578B;&#x9519;&#x8BEF;&#xFF0C;TypeScript&#x7C7B;&#x578B;&#x68C0;&#x67E5;&#x5668;&#x4F7F;&#x7528;<code>Window.onmousedown</code>&#x51FD;&#x6570;&#x7684;&#x7C7B;&#x578B;&#x6765;&#x63A8;&#x65AD;&#x53F3;&#x8FB9;&#x51FD;&#x6570;&#x8868;&#x8FBE;&#x5F0F;&#x7684;&#x7C7B;&#x578B;&#x3002;
&#x56E0;&#x6B64;&#xFF0C;&#x5C31;&#x80FD;&#x63A8;&#x65AD;&#x51FA;<code>mouseEvent</code>&#x53C2;&#x6570;&#x7684;&#x7C7B;&#x578B;&#x4E86;&#x3002;
&#x5982;&#x679C;&#x51FD;&#x6570;&#x8868;&#x8FBE;&#x5F0F;&#x4E0D;&#x662F;&#x5728;&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;&#x7684;&#x4F4D;&#x7F6E;&#xFF0C;<code>mouseEvent</code>&#x53C2;&#x6570;&#x7684;&#x7C7B;&#x578B;&#x9700;&#x8981;&#x6307;&#x5B9A;&#x4E3A;<code>any</code>&#xFF0C;&#x8FD9;&#x6837;&#x4E5F;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#x4E86;&#x3002;</p>
<p>&#x5982;&#x679C;&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;&#x8868;&#x8FBE;&#x5F0F;&#x5305;&#x542B;&#x4E86;&#x660E;&#x786E;&#x7684;&#x7C7B;&#x578B;&#x4FE1;&#x606F;&#xFF0C;&#x4E0A;&#x4E0B;&#x6587;&#x7684;&#x7C7B;&#x578B;&#x88AB;&#x5FFD;&#x7565;&#x3002;
&#x91CD;&#x5199;&#x4E0A;&#x9762;&#x7684;&#x4F8B;&#x5B50;&#xFF1A;</p>
<pre><code class="lang-ts"><span class="hljs-built_in">window</span>.onmousedown = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">mouseEvent: <span class="hljs-built_in">any</span></span>) </span>{
    <span class="hljs-built_in">console</span>.log(mouseEvent.clickTime);  <span class="hljs-comment">//&lt;- Now, no error is given</span>
};
</code></pre>
<p>&#x8FD9;&#x4E2A;&#x51FD;&#x6570;&#x8868;&#x8FBE;&#x5F0F;&#x6709;&#x660E;&#x786E;&#x7684;&#x53C2;&#x6570;&#x7C7B;&#x578B;&#x6CE8;&#x89E3;&#xFF0C;&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;&#x88AB;&#x5FFD;&#x7565;&#x3002;
&#x8FD9;&#x6837;&#x7684;&#x8BDD;&#x5C31;&#x4E0D;&#x62A5;&#x9519;&#x4E86;&#xFF0C;&#x56E0;&#x4E3A;&#x8FD9;&#x91CC;&#x4E0D;&#x4F1A;&#x4F7F;&#x7528;&#x5230;&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;&#x3002;</p>
<p>&#x4E0A;&#x4E0B;&#x6587;&#x5F52;&#x7C7B;&#x4F1A;&#x5728;&#x5F88;&#x591A;&#x60C5;&#x51B5;&#x4E0B;&#x4F7F;&#x7528;&#x5230;&#x3002;
&#x901A;&#x5E38;&#x5305;&#x542B;&#x51FD;&#x6570;&#x7684;&#x53C2;&#x6570;&#xFF0C;&#x8D4B;&#x503C;&#x8868;&#x8FBE;&#x5F0F;&#x7684;&#x53F3;&#x8FB9;&#xFF0C;&#x7C7B;&#x578B;&#x65AD;&#x8A00;&#xFF0C;&#x5BF9;&#x8C61;&#x6210;&#x5458;&#x548C;&#x6570;&#x7EC4;&#x5B57;&#x9762;&#x91CF;&#x548C;&#x8FD4;&#x56DE;&#x503C;&#x8BED;&#x53E5;&#x3002;
&#x4E0A;&#x4E0B;&#x6587;&#x7C7B;&#x578B;&#x4E5F;&#x4F1A;&#x505A;&#x4E3A;&#x6700;&#x4F73;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x7684;&#x5019;&#x9009;&#x7C7B;&#x578B;&#x3002;&#x6BD4;&#x5982;&#xFF1A;</p>
<pre><code class="lang-ts">function createZoo(): Animal[] {
    return [new Rhino(), new Elephant(), new Snake()];
}
</code></pre>
<p>&#x8FD9;&#x4E2A;&#x4F8B;&#x5B50;&#x91CC;&#xFF0C;&#x6700;&#x4F73;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x6709;4&#x4E2A;&#x5019;&#x9009;&#x8005;&#xFF1A;<code>Animal</code>&#xFF0C;<code>Rhino</code>&#xFF0C;<code>Elephant</code>&#x548C;<code>Snake</code>&#x3002;
&#x5F53;&#x7136;&#xFF0C;<code>Animal</code>&#x4F1A;&#x88AB;&#x505A;&#x4E3A;&#x6700;&#x4F73;&#x901A;&#x7528;&#x7C7B;&#x578B;&#x3002;</p>

                                
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